Hominin brain size increase has emerged from within-species encephalization

2024/11/26 by Thomas A. Püschel, Samuel L. Nicholson, Joanna Baker +2 · 1 voice
Earth and Planetary Sciences · Psychology · Social Sciences · #Evolution and Paleontology Studies #Pleistocene-Era Hominins and Archaeology #Primate Behavior and Ecology

paper · pdf · doi:10.1073/pnas.2409542121

openalex publication_date 2024/11/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/25

Abstract

The fact that rapid brain size increase was clearly a key aspect of human evolution has prompted many studies focusing on this phenomenon, and many suggestions as to the underlying evolutionary patterns and processes. No study to date has however separated out the contributions of change through time within vs. between hominin species while simultaneously incorporating effects of body size. Using a phylogenetic approach never applied before to paleoanthropological data, we show that relative brain size increase across ~7 My of hominin evolution arose from increases within individual species which account for an observed overall increase in relative brain size. Variation among species in brain size after accounting for this effect is associated with body mass differences but not time. In addition, our analysis also reveals that the within-species trend escalated in more recent lineages, implying an overall pattern of accelerating relative brain size increase through time.

Citations

• Punctuated equilibria: the tempo and mode of evolution reconsidered
• The Expensive-Tissue Hypothesis: The Brain and the Digestive System in Human and Primate Evolution
• The Expensive Brain: A framework for explaining evolutionary changes in brain size
• General quantitative genetic methods for comparative biology: phylogenies, taxonomies and multi-trait models for continuous and categorical characters
• A Likelihood Approach to Estimating Phylogeny from Discrete Morphological Character Data
• Terrestrial Ecoregions of the World: A New Map of Life on Earth
• RevBayes: Bayesian Phylogenetic Inference Using Graphical Models and an Interactive Model-Specification Language
• The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods

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